JP2017079977A - Ultrasound diagnostic apparatus and ultrasound signal processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To respond to the movement of an ultrasound probe in an ultrasound diagnostic apparatus which evaluates the rigidity of tissue using a shear wave.SOLUTION: Provided is an ultrasound diagnostic apparatus which transmits a push wave and detects the propagation state of a shear wave, comprising: a push pulse transmission unit for transmitting a push pulse; a displacement detection unit for transmitting a detection wave a plurality of times to a subject following the push pulse and receiving a reflection of the detection wave from the subject to detect a displacement of tissue due to a shear wave caused by the push pulse within the subject; an elasticity measurement unit for analyzing the propagation state of the shear wave in a region of interest based on the displacement to measure the elasticity of each tissue within the subject; a probe movement detection unit for detecting the movement speed of an ultrasound probe; and a sequence selection unit for detecting an operation sequence which defines a series of operations cooperated among the push pulse transmission unit, displacement detection unit, and elasticity measurement unit to allow the elasticity measurement unit to measure the elasticity, based on the detection result of the probe movement detection unit.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ultrasonic diagnostic apparatus and an ultrasonic signal processing method, and more particularly to tissue hardness measurement using shear waves.

  In recent years, an ultrasonic diagnostic apparatus having a function of evaluating the hardness of a tissue in a subject has become widespread. There are roughly two methods for evaluating hardness using an ultrasonic diagnostic apparatus. One is that the tissue in the subject is released from the body surface using an ultrasonic probe and then released, and the relative strain of the tissue in the subject is determined based on the magnitude of distortion of the tissue in the subject with respect to the compression. This is a method for evaluating hardness. With this method, it is possible to evaluate the relative hardness within the subject, whether the tissue is harder or softer than the surrounding tissue.

  The other is to generate a shear wave in a region of interest (ROI) set in the subject, and obtain a displacement of the tissue in the region of interest in time series. This is a method for measuring the propagation velocity. Since the propagation speed of the shear wave changes according to the elastic modulus of the tissue, this method can evaluate the absolute hardness (for example, elastic modulus) of the tissue. As a technique for generating a shear wave, for example, the push pulse, which is called ARFI (Acoustic Radiation Force Impulse), is focused on the focus, and the sound pressure of the push pulse, which is an ultrasonic wave, causes the inside of the subject on the focus. A technique for generating displacement in the tissue is used. By using ARFI, it is possible to evaluate the hardness even if the region of interest is a depth that cannot be compressed from the body surface. Therefore, a so-called ultrasonic image (B-mode image) and elasticity generated by evaluating the hardness Image diagnosis using both images is performed.

Special table 2013-544615 gazette

  However, if the ultrasonic probe moves while evaluating the hardness, it becomes difficult to evaluate the hardness. For example, when an ultrasound probe moves when an ultrasound image and an elasticity image are generated at the same time for image diagnosis, the tissue image in the elasticity image and the tissue image in the ultrasound image are the same tissue. It may not be possible to determine whether or not the image is This is because, in order to generate an elastic image, it is necessary to perform push pulse transmission and elastic analysis of shear waves, so the frame rate of the elastic image is very low compared to the ultrasonic image. For this reason, when the ultrasonic probe is moved, a shift of the attention area occurs between the elastic image and the ultrasonic image, and the tissue image in the elastic image and the tissue in the ultrasonic image related to the same tissue are detected. Diagnosis by comparison with images becomes difficult. For example, if the ultrasonic probe moves in the process of acquiring the tissue displacement due to the shear wave in time series, it becomes difficult to detect the displacement. Patent Document 1 discloses a technique for performing correction that eliminates the influence of the movement of the ultrasonic probe from the detected displacement, but sufficient correction is not always possible.

  The present disclosure has been made in view of the above problems, and an object thereof is to provide an ultrasonic diagnostic apparatus that can cope with the movement of an ultrasonic probe.

  An ultrasonic diagnostic apparatus according to one embodiment of the present disclosure uses an ultrasonic probe to physically push a tissue at a specific site by transmitting a push pulse that concentrates the ultrasonic wave on a specific site in a subject. Ultrasound that detects the propagation state of a shear wave having a tissue of a pressed specific site as a vibration source in a region of interest set in the subject by repeatedly transmitting and receiving post-ultrasounds within the subject A diagnostic device, a push pulse transmitter for transmitting a push pulse, and a plurality of detection waves transmitted to the subject following the push pulse, and a plurality of reflected detection waves from the subject corresponding to the detected waves A displacement detection unit that generates a received signal in time series and detects a displacement of tissue in the subject due to a shear wave caused by the push pulse at each reception time of the reflected detection wave; Based on the detection result by the detection unit, the propagation state of the shear wave in the region of interest is analyzed, and the elastic measurement unit that measures the elasticity of each tissue in the subject and the moving speed of the ultrasonic probe are detected. A plurality of operation sequences that define a series of operations in which the push pulse transmission unit, the displacement detection unit, and the elasticity measurement unit cooperate to measure elasticity of the probe movement detection unit and the elasticity measurement unit are held. And a sequence selection unit that selects one operation sequence from a plurality of operation sequences held by the sequence holding unit based on a detection result of the probe movement detection unit. To do.

  According to the present disclosure, with the above-described configuration, the operation sequence for evaluating hardness can be changed based on the moving speed of the ultrasonic probe. Therefore, when the moving speed of the ultrasonic probe is high, for example, an operation sequence that is not affected by the movement of the ultrasonic probe can be selected. On the other hand, when the moving speed of the ultrasonic probe is low, for example, it is possible to select an operation sequence that is affected by the movement of the ultrasonic probe but improves the measurement accuracy. Thereby, the examiner can move the ultrasonic probe without worrying about the operation state of the ultrasonic diagnostic apparatus, and convenience is improved.

1 is a block diagram of an ultrasound diagnostic apparatus 1 according to Embodiment 1. FIG. 3 is a flowchart showing the operation of the entire ultrasound diagnostic apparatus 1 according to the first embodiment. 3 is a flowchart showing a first operation sequence according to the first embodiment. (A) is a schematic diagram which shows the focus position of the push pulse which concerns on a 1st operation | movement sequence. (B) is a schematic diagram showing a focal position of a push pulse according to a second operation sequence. It is a schematic diagram which shows the mode of generation | occurrence | production and propagation of a shear wave. 6 is a schematic diagram illustrating an operation of shear wave propagation analysis according to Embodiment 1. FIG. (A) is a schematic diagram which shows the speed measurement of a shear wave. (B) is a schematic diagram which shows an example of an elasticity image. (A-1)-(a-4) is a schematic diagram which shows the propagation analysis result for every sub sequence which concerns on a 1st operation | movement sequence. (B) is a schematic diagram which shows the propagation analysis result for every operation | movement sequence. (C) is a schematic diagram which shows an example of the weighting coefficient in integration of a propagation analysis result. (D-1)-(d-2) is a schematic diagram which shows the propagation analysis result for every sub sequence which concerns on a 2nd operation | movement sequence. 6 is a flowchart showing a second operation sequence according to the first embodiment. 6 is a flowchart showing the operation of the entire ultrasonic diagnostic apparatus according to the second embodiment. 10 is a flowchart showing a third operation sequence according to the second embodiment. (A-1) and (a-2) are schematic diagrams of detection wave transmission when the detection wave is a plane wave. (B-1) and (b-2) are schematic diagrams of detection wave transmission when the detection wave is a focal wave. (C-1) and (c-2) are schematic diagrams in the case of receiving reflected detection waves sparsely in time. 10 is a flowchart showing a third operation sequence according to a modification of the second embodiment. 10 is a flowchart illustrating the operation of the entire ultrasound diagnostic apparatus according to the third embodiment. 10 is a flowchart showing a fourth operation sequence according to the third embodiment. (A), (b) is a schematic diagram which shows the case where an attention area | region does not correspond with a tomographic image signal and a reference | standard tomographic image signal. (C) is a schematic diagram which shows the displacement detection operation | movement which concerns on a 1st operation | movement sequence. (D) is a schematic diagram which shows the displacement detection operation | movement which concerns on a 4th operation | movement sequence. 10 is a flowchart showing the operation of the entire ultrasonic diagnostic apparatus according to the fourth embodiment. 10 is a flowchart showing a fifth operation sequence according to the fourth embodiment. It is a flowchart which shows operation | movement of the whole ultrasound diagnosing device which concerns on the other modification (1).

≪Background to the form for carrying out the invention≫
The inventor conducted various studies to cope with the movement of the ultrasonic probe in the ultrasonic diagnostic apparatus that evaluates the hardness of the tissue using a shear wave.
In an ultrasonic diagnostic apparatus that evaluates the hardness of a tissue using a shear wave, there are a plurality of influences due to the movement of the ultrasonic probe, and therefore, problems in each influence will be described below.

  First, an ultrasonic diagnostic apparatus that evaluates the hardness of a tissue displays an elastic image that expresses the distribution of hardness in a region of interest in color, or displays an elastic image on an ultrasonic image that uses the same region as a region of interest. In general, a superimposed display is performed. Here, the ultrasonic image is, for example, a B-mode tomographic image. Rather than expressing the hardness at each position in the region of interest numerically, this is a visual representation of the shape of the tissue that differs in hardness from the surroundings, and how hard it is. This is because it is easier for the inspector to show. In addition, by comparing the ultrasound image with the same region as the region of interest, the examiner can know how the tissue is reflected in the ultrasound image, which helps diagnosis. is there. On the other hand, as described above, since the time required for transmitting the push pulse and the elastic analysis of the shear wave is large, the frame rate of the elastic image is significantly lower than the frame rate of the ultrasonic image. For this reason, when the ultrasonic probe moves at a certain speed or more, the region of interest does not match between the elastic image and the ultrasonic image, and the tissue images cannot be correctly associated with each other. The reason will be described below. In both the ultrasound image and the elasticity image, when the ultrasound probe moves between the start and end of image generation, the region within the actual subject where ultrasound is transmitted and received, that is, ultrasound The area that the diagnostic apparatus processes as the area of interest does not match the area that the inspector has attempted to acquire information, that is, the inspection target area that the inspector assumes. This is because the ultrasound diagnostic apparatus sets the region of interest as a relative position based on the position and orientation of the ultrasound probe, so that the region of interest also interlocks when the position or orientation of the ultrasound probe changes. Because it moves. When the moving speed of the ultrasonic probe is the same, the lower the frame rate, the larger the moving amount of the ultrasonic probe between frames. Naturally, the lower the frame rate, the larger the moving amount of the region of interest. Therefore, even if the inspector sets the region of interest so that the inspection target region is the same between the ultrasonic image and the elastic image, the amount of movement of the region of interest differs between the ultrasonic image and the elastic image. The region of interest does not match with the elastic image. Therefore, the coordinates in the elasticity image and the same coordinates in the ultrasound image do not necessarily correspond to the same location in the subject, and the tissue image in the elasticity image and the tissue image in the ultrasound image The images acquired from the same tissue cannot be associated with each other.

In view of the above problems, the inventor has studied a technique for improving the frame rate of an elastic image.
In addition, an ultrasonic diagnostic apparatus that evaluates tissue hardness detects displacement in a region of interest. As a method for detecting displacement, in the process of shear wave propagation, ultrasonic waves are repeatedly transmitted and received, and each received signal acquired in time series and a reference signal acquired at a time when no displacement has occurred. There are a method based on an absolute difference and a method based on a relative difference (time change amount of an absolute difference) between received signals acquired in time series. In the method based on the relative difference, even if the ultrasonic probe moves, the overlap area of the region of interest between the received signals does not become too small. There is a problem that accuracy is likely to decrease. On the other hand, in the method based on the absolute difference, it is easy to improve the accuracy of the displacement amount. On the other hand, when the attention area shifts between the received signal and the reference signal, the area in which the displacement cannot be calculated becomes wider as the deviation of the attention area increases. There is. Conventionally, during the evaluation of tissue hardness, detection of displacement based on absolute difference is performed on the assumption that the ultrasonic probe does not move, but if the moving speed of the ultrasonic probe is fast, the displacement is calculated. Since the area where it cannot be widened, an area where the elasticity of the tissue cannot be evaluated may occur.

In view of the above problems, the inventor has studied a technique for changing the displacement calculation method in accordance with the moving speed of the ultrasonic probe.
Further, the inventor considered that the state in which the moving speed of the ultrasonic probe is high is not suitable for generating the various problems described above and evaluating the hardness of the tissue. When the moving speed is higher than a predetermined speed, a technique that does not start generating an elastic image until the moving speed of the ultrasonic probe is lower than the predetermined speed was examined.

Based on the above examination, the inventor obtained the idea of changing a part of the tissue hardness evaluation operation in accordance with the moving speed of the ultrasonic probe, and corresponds to the ultrasonic diagnostic apparatus according to the embodiment. It came to do.
Hereinafter, an ultrasonic diagnostic apparatus according to an embodiment will be described in detail with reference to the drawings.
<< Embodiment 1 >>
FIG. 1 shows a block diagram of the ultrasonic diagnostic apparatus 1 according to the first embodiment. The ultrasonic diagnostic apparatus 1 includes a control unit 11, a shear wave excitation unit 12, an ultrasonic signal acquisition unit 13, a displacement detection unit 14, a propagation analysis unit 15, a probe movement detection unit 16, a sequence selection unit 17, and a tomographic image storage. Unit 18, displacement amount storage unit 19, sequence holding unit 20, and elastic image storage unit 21. Further, the control unit 11 is configured to be connectable with the ultrasonic probe 2 and the display unit 3. FIG. 1 shows a state in which an ultrasonic probe 2 and a display unit 3 are connected to the ultrasonic diagnostic apparatus 1.

  The ultrasonic probe 2 has, for example, a plurality of transducers (not shown) arranged in a one-dimensional direction. Each vibrator is made of, for example, PZT (lead zirconate titanate). The ultrasonic probe 2 is an electric signal generated by the shear wave excitation unit 12 (hereinafter referred to as “ARFI driving signal”) or an electric signal generated by the ultrasonic signal acquisition unit 13 (hereinafter “transmission”). (Referred to as “driving signal”) from the control unit 11 and converted into ultrasonic waves. The ultrasound probe 2 is converted from the ARFI drive signal or the transmission drive signal in a state where the outer surface of the ultrasound probe 2 on the transducer side is in contact with the surface of the subject's skin, etc. An ultrasonic beam composed of a plurality of ultrasonic waves emitted from is transmitted toward the measurement target in the subject. The ultrasonic probe 2 receives a plurality of reflected detection waves from the measurement target with respect to the transmission detection wave based on the transmission drive signal, and each of the reflected detection waves is transmitted to an electric signal (hereinafter, “ The element reception signal is supplied to the ultrasonic signal acquisition unit 13 via the control unit 11.

  The shear wave excitation unit 12 generates an ARFI drive signal that is an electrical signal for causing the ultrasonic probe 2 to send a push pulse. The push pulse is a pulsed ultrasonic wave for causing displacement in the tissue in the subject in order to generate a shear wave in the subject. Specifically, it is an ultrasonic wave having a larger wave number than a transmission detection wave, which will be described later, focusing on a certain region in the region of interest in the subject. Therefore, the ARFI drive signal is a pulsed electric signal generated so that the ultrasonic wave transmitted from each vibration element constituting the ultrasonic probe 2 reaches the focal point. The shear wave excitation unit 12 receives, from the control unit 11, a focal position for each push pulse specified in an operation sequence described later, a transducer used for transmission, a wave number, a transmission time length, and the like, and an ARFI drive signal based on the operation sequence Is generated.

  The ultrasonic signal acquisition unit 13 generates a transmission drive signal that is an electric signal for causing the ultrasonic probe 2 to transmit a transmission detection wave. The transmission drive signal is generated so that, for example, the transmission detection wave transmitted from each vibration element constituting the ultrasonic probe 2 becomes a plane wave traveling in a specific direction, and the timing is aligned for each vibration element. Or, it is a pulse-like electric signal in which the operation timing is shifted stepwise at a fixed pitch from one end of the transducer array to the other end. Alternatively, the transmission drive signal is generated for each vibration element, for example, so that the transmission detection wave transmitted from each vibration element constituting the ultrasonic probe 2 becomes a focal wave that simultaneously reaches the transmission focus point. It may be a pulse-shaped electric signal with different. The ultrasonic signal acquisition unit 13 performs phasing addition on the element reception signal based on the reflected detection wave to generate an acoustic line signal. When the transmission detection wave is a plane wave, the transmission detection wave is transmitted so as to spread over the entire region of interest, and an acoustic line signal of the entire region of interest is generated based on the reflected ultrasound. On the other hand, when the transmission detection wave is a focal wave, the acoustic line signal based on the reflected ultrasonic wave is a part of the region through which the transmission detection wave has passed. It is generated for the divided area. Therefore, when the transmission detection wave is a focal wave, transmission of the transmission detection wave and reception of the reflection detection wave are repeatedly performed while moving the transmission focus point in the element array direction in order to obtain an acoustic line signal of the entire region of interest. . The ultrasonic signal acquisition unit 13 outputs the generated acoustic line signal to the tomographic image storage unit 18 via the control unit 11.

  The displacement detection unit 14 includes a plurality of acoustic line signals (hereinafter referred to as “tomographic image signals”) related to one tomographic image that is a target of displacement detection, and a plurality of acoustic line signals related to one reference tomographic image. (Hereinafter referred to as “reference tomographic image signal”) is acquired from the tomographic image storage unit 18 via the control unit 11. The reference tomographic image signal is used to extract a displacement due to a shear wave from the tomographic image signal. Specifically, the reference tomographic image signal is a tomographic image signal obtained by imaging a region of interest before the push pulse is transmitted. Then, the displacement detector 14 detects the displacement of each pixel of the tomographic image signal from the difference between the tomographic image signal and the reference tomographic image signal, and associates the displacement with the coordinates of each pixel to generate a displacement image. The displacement detection unit 14 outputs the generated displacement image to the displacement amount storage unit 19 via the control unit 11.

  The propagation analysis unit 15 acquires a displacement image from the displacement amount storage unit 19 via the control unit 11. The propagation analysis unit 15 detects the position, traveling direction, and velocity of the shear wave wavefront at each time when the displacement image is acquired from the displacement image, and calculates the elastic modulus of the subject tissue corresponding to each pixel of the displacement image. Then, an elastic image is generated. The propagation analysis unit 15 outputs the generated elasticity image to the elasticity image storage unit 21 via the control unit 11.

  The probe movement detection unit 16 detects the moving speed of the ultrasonic probe 2 and outputs it to the sequence selection unit 17. Specifically, the probe movement detection unit 16 acquires the latest tomographic image signal and the previous tomographic image signal from the tomographic image storage unit 18, and based on the difference between them, the probe 2 detects the ultrasonic probe 2. Detect the moving speed. The moving speed of the ultrasound probe 2 is calculated by, for example, calculating the difference (displacement) between the latest tomographic image signal and the immediately preceding tomographic image signal for each pixel, and reducing the tomographic value to the minimum value of the difference for each pixel. It can be calculated by multiplying the frame rate of the image. Note that other representative values such as an intermediate value may be used instead of the minimum difference value for each pixel. For example, a shear wave such as a position where only the focal position and depth of the push pulse greatly differ cannot pass. The moving speed of the ultrasound probe 2 may be calculated using the difference in the pixel corresponding to the place. Alternatively, when calculating the difference (displacement), only the difference (displacement) in the arrangement direction component of the elements may be detected. This is because the displacement due to the shear wave occurs in the depth direction in principle, and therefore the difference (displacement) in the arrangement direction of the elements is highly likely due to the movement of the ultrasonic probe 2. The method for detecting the moving speed of the ultrasonic probe 2 is not limited to the above-described method, and any method using a tomographic image signal may be used. Alternatively, for example, the ultrasonic probe 2 may further include a speed sensor, and the probe movement detection unit 16 may use a detection value of the speed sensor. Alternatively, for example, the ultrasonic diagnostic apparatus 1 further includes a camera for detecting the movement of the ultrasonic probe 2, and the ultrasonic probe 2 uses the camera to determine the position and orientation of the ultrasonic probe 2. The probe movement detection unit 16 may detect the movement speed of the ultrasonic probe 2 by detecting the movement of the marker from the image acquired by the camera.

  The sequence selection unit 17 uses the movement speed of the ultrasonic probe 2 detected by the probe movement detection unit 16 to select one operation sequence from among a plurality of operation sequences held by the sequence holding unit 20. select. Here, the operation sequence refers to a series of operations of the ultrasonic diagnostic apparatus 1 for generating one elastic image. Specifically, the operation sequence is performed every time one or more push pulses are transmitted and each push pulse is transmitted. Transmission of the detected wave, reception of the reflected detection wave, and propagation analysis. That is, the operation sequence defines a series of operations in which the shear wave excitation unit 12, the ultrasonic signal acquisition unit 13, the displacement detection unit 14, and the propagation analysis unit 15 cooperate. The operation sequence includes, for example, the number of push pulse transmissions, the focus position for each push pulse, the transducer / wave number used for transmission or the transmission time length, information on whether the detection wave is a plane wave or a focus wave, and the detection wave is a plane wave. If there is a transmission direction, if the detected wave is a focal wave, the number of transmission focus points, the position of each transmission focus point, the acoustic signal generation area corresponding to the position of each transmission focus point, the frame rate of the tomographic image signal Etc. are included. Note that the operation sequence may further include information defining an operation associated with a series of operations such as transmission of the detection wave, reception of the reflection detection wave, and propagation analysis described above. For example, whether to generate an elastic image or not. Alternatively, information such as the display form of the elastic image may be included.

The control unit 11 outputs the tomographic image generated by the ultrasonic signal acquisition unit 13 and the elasticity image generated by the propagation analysis unit 15 to the display unit 3 in addition to the control of each component as described above. In addition, when outputting an elasticity image to the display part 3, the control part 11 performs geometric transformation, and when outputting a tomographic image to the display part 3, the control part 11 performs envelope detection, logarithmic compression, etc. in addition to geometric transformation. I do.
The tomographic image storage unit 18, the displacement amount storage unit 19, the sequence holding unit 20, and the elastic image storage unit 21 store a tomographic image, a displacement image, operation sequence data, and elastic image data, respectively. Each of the tomographic image storage unit 18, the displacement amount storage unit 19, the sequence holding unit 20, and the elastic image storage unit 21 is realized by a storage medium such as a RAM, a flash memory, a hard disk, and an optical disk. Note that two or more of the tomographic image storage unit 18, the displacement amount storage unit 19, the sequence holding unit 20, and the elastic image storage unit 21 may be realized by a single storage medium. Alternatively, the tomographic image storage unit 18, the displacement amount storage unit 19, the sequence holding unit 20, and the elastic image storage unit 21 may be realized inside other elements of the ultrasonic diagnostic apparatus 1, for example, the sequence holding unit 20. May be part of the sequence selector 17. In addition, one or more of the tomographic image storage unit 18, the displacement amount storage unit 19, the sequence holding unit 20, and the elastic image storage unit 21 are configured outside the ultrasonic diagnostic apparatus 1 and have interfaces such as USB, eSATA, and SDIO. It may be connected to the ultrasonic diagnostic apparatus 1 via the network, or may be a resource configured to be accessible from the ultrasonic diagnostic apparatus 1 via a network, for example, a file server or NAS (Network Attached Storage).

  Each of the control unit 11, the shear wave excitation unit 12, the ultrasonic signal acquisition unit 13, the displacement detection unit 14, the propagation analysis unit 15, the probe movement detection unit 16, and the sequence selection unit 17 includes, for example, an FPGA (Field Programmable Gate). Array) and hardware such as ASIC (Application Specific Integrated Circuit). Two or more of these may be configured as a single element. For example, the shear wave excitation unit 12 and the ultrasonic signal acquisition unit 13 may be realized as one configuration. In this case, the shear wave excitation unit 12 is configured using the configuration of the ultrasonic signal acquisition unit 13 by generating the ARFI drive signal using the same configuration as the configuration for generating the transmission drive signal of the ultrasonic signal acquisition unit 13. Can be realized. A part or all of these may be realized by a single FPGA or ASIC. In addition, these may be implemented individually or in a group of two or more by a memory, a programmable device such as a CPU (Central Processing Unit), a GPGPU (General Purpose Graphic Processing Unit), and software.

<Operation>
The operation of the ultrasonic diagnostic apparatus 1 according to Embodiment 1 will be described. FIG. 2 is a flowchart showing the overall operation of the ultrasound diagnostic apparatus 1.
First, ultrasonic waves are transmitted to and received from the subject, and the acquired received signal is stored (step S10). Specifically, the operation is as follows. First, a transmission event is performed as follows. First, the ultrasonic signal acquisition unit 13 generates a pulsed transmission signal. Next, the ultrasonic signal acquisition unit 13 performs transmission beam forming for setting a delay time for each element of the ultrasonic probe 2 on the transmission signal, and corresponds to each element of the ultrasonic probe 2. A plurality of transmission drive signals are generated. Each transducer of the ultrasonic probe 2 converts a corresponding transmission drive signal into an ultrasonic wave, so that an ultrasonic beam is transmitted into the subject. Next, each transducer of the ultrasound probe 2 acquires the reflected ultrasound reflected from within the subject and converts it into an element reception signal. The ultrasonic signal acquisition unit 13 performs phasing addition on the element reception signal to generate an acoustic line signal. The control unit 11 acquires an acoustic line signal from the ultrasonic signal acquisition unit 13 for each transmission event, and stores a plurality of acoustic line signals constituting one tomographic image in the tomographic image storage unit 18.

  Next, the moving speed of the ultrasonic probe 2 is detected (step S20). Specifically, the probe movement detection unit 16 acquires the acoustic line signal related to the latest transmission event and the acoustic line signal related to the transmission event immediately before from the tomographic image storage unit 18, The difference (displacement) is detected by correlation processing. For example, the probe movement detection unit 16 can calculate the moving speed of the ultrasonic probe 2 by multiplying the representative value such as the minimum value or the intermediate value of the difference by the execution time difference of the transmission event. .

  Next, an operation sequence is determined (steps S30 and S40). Specifically, the sequence selection unit 17 determines whether or not the moving speed of the ultrasound probe 2 exceeds a predetermined threshold value (step S30). Here, the predetermined threshold is, for example, 10 mm / s. When the moving speed of the ultrasound probe 2 is equal to or lower than the predetermined threshold (No in S30), the sequence selection unit 17 selects the first operation sequence similar to that of the conventional ultrasound diagnostic apparatus (step S40). In this first operation sequence, the region of interest is divided into n (n is an integer of 2 or more) small regions, and each small region is transmitted by one transmission of a push pulse and subsequent transmission / reception of a plurality of detection waves. Shear wave propagation analysis is performed (these are collectively referred to as “subsequence”), and an elastic image is generated by synthesizing the propagation analysis results of n subsequences. Hereinafter, the case where n = 4 will be described. On the other hand, when the moving speed of the ultrasound probe 2 is faster than the predetermined threshold (Yes in S30), the sequence selection unit 17 selects the second operation sequence (Step S41). In this second sequence, in order to improve the frame rate of the elastic image, the region of interest is divided into m small regions (m is an integer greater than or equal to 1 and smaller than n), and each small region is subjected to propagation analysis by a subsequence. Then, an elastic image is generated by synthesizing the propagation analysis results of m subsequences. Hereinafter, the case where m = 2 will be described.

Next, an operation sequence is executed (steps S50 and S60).
Here, only step S50 will be described, and the difference of step S60 from step S50 will be described later. FIG. 3 is a flowchart showing a detailed operation according to the operation sequence of S50.
First, the control unit 11 sets a region of interest (step S410). The method of setting the region of interest includes, for example, displaying the latest tomographic image recorded in the tomographic image storage unit 18 on the display unit 3 and providing the examiner with an input unit (not shown) such as a touch panel, a mouse, or a trackball. Specify the area of interest. Note that the method of setting the attention area is not limited to this case. For example, the entire area of the tomographic image may be set as the attention area, or a certain range including the central portion of the tomographic image may be set as the attention area. Further, when setting the region of interest, a tomographic image may be acquired again.

Next, ultrasonic waves are transmitted to and received from the region of interest, and the acquired received signal is stored as a reference signal (step S420). Specifically, a transmission event is performed, and a plurality of acoustic line signals constituting one tomographic image are stored in the tomographic image storage unit 18 as reference tomographic image signals.
Subsequently, a sub-sequence including transmission of push pulses, subsequent transmission / reception of detection waves, and shear wave propagation analysis is executed. First, the first sub-sequence (steps S441 to S444 related to i = 1) is executed (step S430).

  In the first sub-sequence, first, a push pulse is transmitted (step S441). Specifically, the shear wave excitation unit 12 generates a pulse based on the focal position of the push pulse defined as the first push pulse in the first operation sequence, the vibrator used for transmission, the wave number, or the transmission time length. To generate a shaped ARFI signal. Next, the shear wave excitation unit 12 performs transmission beam forming for setting the delay time for each element of the ultrasonic probe 2 with respect to the ARFI signal, and a plurality of elements corresponding to each element of the ultrasonic probe 2. The ARFI driving signal is generated. The focal position of the first push pulse is, for example, the center of one small region obtained by dividing the region of interest into n parts (here, four parts) in the column direction of the transducers. A specific example will be described with reference to FIG. In FIG. 4A, the x direction is the column direction of the transducers, and the y direction is the depth direction. At this time, the region of interest 401 is divided into four small regions 402, 403, 404, and 405, and the first push pulse is transmitted so as to be focused on the focal position 412 inside the small region 402. Each transducer of the ultrasonic probe 2 converts a corresponding transmission drive signal into an ultrasonic wave, so that a push pulse is transmitted into the subject.

  Here, the generation of the shear wave by the push pulse will be described with reference to the schematic diagrams of FIGS. FIG. 5A is a schematic diagram showing the tissue before the push pulse application in the in-subject region corresponding to the region of interest. 5A to 5E, each “◯” indicates a part of the tissue in the subject in the region of interest, and the broken line indicates the center position of the tissue “O” when there is no load. Each is shown. Here, when a push pulse was applied to the focal point 101 in a state where the ultrasonic probe 2 was in close contact with the skin surface 100, it was located at the focal point 101 as shown in the schematic diagram of FIG. The tissue 132 moves by being pushed in the traveling direction of the push pulse. Further, the tissue 133 on the travel direction side of the push pulse from the tissue 132 is pushed by the tissue 132 and moves in the travel direction of the push pulse. Next, when the transmission of the push pulse is completed, the tissues 132 and 133 try to restore the original positions. Therefore, as shown in the schematic diagram of FIG. 5C, the tissues 131 to 133 move in the traveling direction of the push pulse. Start vibration along. Then, as shown in the schematic diagram of FIG. 5D, the vibration propagates to the tissues 121 to 123 and the tissues 141 to 143 adjacent to the tissues 131 to 133. Furthermore, as shown in the schematic diagram of FIG. 5E, the vibration further propagates to the tissues 111 to 113 and the tissues 151 to 153. Accordingly, vibration propagates in the direction orthogonal to the direction of vibration in the subject. That is, a shear wave is generated at the place where the push pulse is applied and propagates through the subject.

  Returning to FIG. 3, the description will be continued. Next, ultrasonic waves are transmitted / received to / from the region of interest multiple times, and the acquired plural ultrasonic signals are stored (step S442). Specifically, immediately after the end of the transmission of the push pulse, for example, the same operation as step S10 is repeated 10,000 times per second. As a result, the tomographic image of the subject is repeatedly acquired immediately after the generation of the shear wave until the propagation ends.

  Next, the displacement of each pixel is detected (step S443). Specifically, first, the displacement detection unit 14 acquires the reference tomographic image signal stored in the tomographic image storage unit 18 in step S420. Next, the displacement detection unit 14 receives the reflected detection wave related to the tomographic image signal from the difference from the reference tomographic image signal for each tomographic image signal stored in the tomographic image storage unit 18 in step S442. The displacement of each pixel is detected. More specifically, for example, by performing correlation processing between the tomographic image signal and the reference tomographic image signal, a search is made for which pixel on the tomographic image signal corresponds to which pixel on the reference tomographic image signal. The coordinate difference is specified as a displacement corresponding to the pixel on the tomographic image signal. The displacement detection method is not limited to the correlation processing, and any technique for detecting the amount of motion between two tomographic image signals, such as pattern matching, may be used. As an example of pattern matching, for example, the tomographic image signal is divided into regions of a predetermined size such as 8 pixels × 8 pixels, and each region and the reference tomographic image signal are subjected to pattern matching, whereby each of the tomographic image signals Pixel displacement can be detected. As a pattern matching method, for example, a difference between luminance values is calculated for each corresponding pixel between each region and a reference region of the same size in the reference tomographic image signal, and a sum of absolute values thereof is calculated. For the combination of the region having the smallest total value and the reference region, the region and the reference region are assumed to be the same region, and the reference point of the region (for example, the upper left corner) and the reference point of the reference region The distance is detected as a displacement. Note that the area of the predetermined size may be another size, and instead of the total absolute value of the luminance value differences, for example, a total square value of the luminance value differences may be used. . Further, when detecting displacement by correlation processing or pattern matching, a difference in y-coordinate (depth difference) between corresponding pixels may be used as the magnitude of displacement instead of the coordinate difference between corresponding pixels. This is because the shear wave propagation direction is in principle the element array direction (x direction), so the displacement due to the shear wave is a direction perpendicular to the propagation direction, and in principle the depth direction (y direction). is there. By the above processing, how much the tissue of the subject corresponding to each pixel of each tomographic image signal has moved by the push pulse or the shear wave is calculated as a displacement. The displacement detection unit 14 generates a displacement image by associating the displacement of each pixel related to one tomographic image with the coordinates of the pixel, and outputs the generated displacement image to the displacement amount storage unit 19.

Next, shear wave propagation analysis is performed (step S444). Specifically, a wavefront image is generated by extracting the wavefront of the shear wave from each displacement image. From this wavefront image, the position, amplitude, traveling direction and speed of the wavefront can be easily detected. The generation of the wavefront image is performed by, for example, a procedure for extracting a displacement region, thinning processing, spatial filtering, and temporal filtering.
Specific processing will be described with reference to FIG. FIG. 6A shows an example of a displacement image. As in FIG. 5, “◯” in the figure indicates a part of the tissue in the subject in the region of interest, and the position before the push pulse is applied is an intersection of broken lines. The propagation analysis unit 15 extracts a region where the displacement amount δ is large by using a dynamic threshold with the displacement amount δ as a function of the coordinate x for each y coordinate. For each x coordinate, the displacement amount δ is used as a function of the coordinate y and a dynamic threshold is used to extract a region exceeding a certain threshold as a region having a large displacement amount δ. The dynamic threshold is to determine the threshold by performing signal analysis or image analysis on the target region. The threshold value is not a constant value, but varies depending on the signal width and maximum value of the target region. FIG. 6A shows a graph 211 in which the displacement amount on the straight line 210 with y = y ₁ is plotted, and a graph 221 in which the displacement amount on the straight line 220 with x = x ₁ is plotted. Thereby, for example, the displacement region 230 in which the displacement amount δ is larger than the threshold value can be extracted.

  Next, the propagation analysis unit 15 performs a thinning process on the displacement region and extracts a wavefront. The displacement areas 240 and 250 shown in the schematic diagram of FIG. 6B are areas extracted as displacement areas in step S52. The propagation analysis unit 15 extracts a wavefront using, for example, a thinning algorithm of Hilditch. For example, in the schematic diagram of FIG. 6B, the wavefront 241 is extracted from the displacement region 240 and the wavefront 251 is extracted from the displacement region 250. Note that the thinning algorithm is not limited to Hilditch, and any thinning algorithm may be used. Further, for each displacement area, the process of removing coordinates having a displacement amount δ equal to or less than the threshold value from the displacement area may be repeated while increasing the threshold value until the displacement area becomes a line having a width of 1 pixel.

  Next, the propagation analysis unit 15 performs spatial filtering on the wavefront image data after the thinning process, and removes a wavefront having a short length. For example, the length of each wavefront extracted in step S53 is detected, and the wavefront having a length shorter than ½ of the average value of all the wavefront lengths is deleted as noise. Specifically, as shown in the wavefront image of FIG. 6C, the average value of the lengths of the wavefronts 261 to 264 is calculated, and the shorter wavefronts 263 and 264 are eliminated as noise. Thereby, the erroneously detected wavefront can be erased.

The propagation analysis unit 15 performs displacement region extraction, thinning processing, and spatial filtering operations on all displacement images. As a result, wavefront image data is generated one-to-one with respect to the displacement image.
Finally, the propagation analysis unit 15 performs time filtering on the plurality of wavefront image data to remove wavefronts that are not propagated. Specifically, a time change of the wavefront position is detected in two or more wavefront images that are temporally continuous, and a wavefront having an abnormal velocity is removed as noise. Propagation analysis unit 15, for example, the wavefront image 270 at time t = t _1, the wavefront image 280 at time t = t ₁ + Δt, between the wavefront image 290 at time t = t ₁ + 2Δt, the time change of the wavefront position To detect. For example, with respect to the wavefront 271, a region 276 in which a shear wave can move between Δt in the wavefront image 280 in the direction perpendicular to the wavefront (in the x-axis direction in FIG. 6) around the same position as the wavefront 271. Thus, correlation processing with the wavefront 271 is performed. At this time, correlation processing is performed within a range including both the positive direction (right side in the figure) and the negative direction (left side in the figure) of the wavefront 271. This is to detect both transmitted waves and reflected waves. Thereby, it is detected that the movement destination of the wavefront 271 is the wavefront 281 in the wavefront image 280, and the movement distance of the wavefront 271 at the time Δt is calculated. Similarly, for each of the wavefronts 272 and 273, correlation processing is performed in a region where the shear wave can move between Δt in the direction perpendicular to the wavefront with the same position as the wavefront in the wavefront image 280 as the center. Accordingly, it is detected that the wavefront 272 has moved to the position of the wavefront 283 and the wavefront 273 has moved to the position of the wavefront 282, respectively. The same processing is performed between the wavefront image 280 and the wavefront image 290 to detect that the wavefront 281 has moved to the wavefront 291 position, the wavefront 282 to the wavefront 292 position, and the wavefront 283 to the wavefront 293 position, respectively. To do. Here, the traveling distance of one wavefront indicated by the wavefront 273, the wavefront 282, and the wavefront 292 is significantly smaller than the other wavefronts (the propagation speed is extremely slow). Since such a wavefront is likely to be a false detection, it is eliminated as noise. Thereby, as shown in the wavefront image 300 of FIG.6 (e), the wavefronts 301 and 302 can be detected.

The propagation analysis unit 15 calculates the position and velocity of the wavefront using the generated wavefront image data for each time and the wavefront correspondence information. Here, the wavefront correspondence information is information indicating which wavefront of each wavefront image corresponds to the same wavefront. For example, in FIG. 6D, the wavefront 272 has moved to the position of the wavefront 283. Is detected, this is information that the wavefront 283 and the wavefront 272 are the same wavefront. Hereinafter, wavefront velocity calculation will be described with reference to FIG. FIG. 7A is a combination of a wavefront image at a certain time t ₁ and a wavefront image at a time t ₂ (t ₁ <t ₂ ) as one wavefront image 310. Here, it is assumed that there is correspondence information indicating that the wavefront 311 at time t ₁ and the wavefront 312 at time t ₂ are the same wavefront. The propagation analysis unit 15 detects the coordinates (x _t2 , _yt2 ) on the wavefront 312 corresponding to the coordinates (x _t1 , _yt1 ) on the wavefront 311 from the correspondence information. Accordingly, it can be estimated that the shear wave that has passed the coordinates (x _t1 , y _t1 ) at time t ₁ has reached the coordinates (x _t2 , y _t2 ) at time t ₂ . Therefore, the coordinates (x _t1, y _t1) to pass the shear wave velocity v (x _t1, y _t1), the distance d between the coordinates (x _t1, y _t1) and the coordinates (x _t2, y _t2) Can be estimated as a value obtained by dividing the required time Δt = t ₂ −t ₁ . That is, v (x _t , y _t ) = d / Δt = √ {(x _t2 −x _t1 ) ² + (y _t2 −y _t1 ) ² } / Δt. The propagation analysis unit 15 performs the above-described processing on all wavefronts, acquires the shear wave velocity for all coordinates through which the wavefront has passed, and holds this.

Returning to FIG. 3, the description will be continued. With the above operation, the first sub-sequence is completed. After completion of the first sub-sequence, all sub-sequences are not completed (Yes in step S445), so the second sub-sequence is executed (step S446).
Next, the second sub-sequence is executed. In the second sub-sequence, the same operation as in the first sub-sequence is performed except for the characteristics of the push pulse transmitted in step S441. In the transmission of the push pulse according to the second sub-sequence (i = 2 in step S441), the push pulse is applied to one center of a small area different from the first sub-sequence, for example, the focal position 422 in FIG. Send. Since the operations in steps S442 to S444 are the same as those in the first sub-sequence, description thereof is omitted.

  Thereafter, similarly, the third sub-sequence and the fourth sub-sequence are executed. Similarly, in the third sub-sequence, in the transmission of the push pulse (i = 3 in step S441), one center of a small area different from both the first sub-sequence and the second sub-sequence, for example, FIG. The push pulse is transmitted to the focal position 432 in FIG. Similarly, in the fourth sub-sequence, in the push pulse transmission (i = 4 in step S441), one center of a small area different from any of the first to third sub-sequences, for example, FIG. A push pulse is transmitted to the focal position 442 in (a).

After the processing of all subsequences is completed (No in step S445), the propagation analysis unit 15 integrates the propagation analysis results (step S450). Specifically, the direction and speed of the shear wave calculated for each subsequence are totaled, and the direction and speed of the shear wave at each coordinate of the region of interest are calculated. This will be described with reference to the schematic diagram of FIG. FIGS. 8A-1 to 8A-4 show the positional relationship between the region of interest, the shear wave velocity distribution, and the focus of the push pulse in the first to fourth subsequences, respectively. . For example, in the velocity distribution diagram 410 in FIG. 8A-1, the focus position 412 of the push pulse exists near the left end of the region of interest 411, and the region 413 where the propagation velocity of the shear wave is high is detected. Similarly, in the velocity distribution diagram 420 in FIG. 8A-2, the focus position 422 of the push pulse exists on the left side of the region of interest 421, and the region 423 where the shear wave propagation velocity is high is detected. Further, in the velocity distribution diagram 430 in FIG. 8A-3, the focal position 432 of the push pulse exists on the right side of the region of interest 431, and the region 433 where the shear wave propagation velocity is high is detected. Similarly, in the velocity distribution diagram 440 in FIG. 8A-4, the focus position 442 of the push pulse exists near the right end of the region of interest 441, and the region 443 where the shear wave propagation velocity is high is detected. The regions 413, 423, 433, and 443 where the shear wave propagation speed is high actually correspond to one tissue, but due to the attenuation of the shear wave, the portion closer to the focus position of the push pulse is the other region. On the other hand, the boundary with the other region may be unclear for the portion far from the focal position of the push pulse, while the boundary with the region is clear. These are integrated to create one velocity distribution diagram 450 as shown in FIG. Specifically, for each coordinate, the shear wave velocity is acquired from each of the velocity distribution diagrams 410, 420, 430, and 440, and a representative value is calculated. As a representative value calculation method, for example, a weighted average, a maximum value, or the like may be used, or invalid data (for example, acquired from other speed distribution diagrams in which no speed is acquired and there is no value). It is also possible to use an average value excluding a large difference with any of the speeds. When the weighted average is used, the weighting coefficient a _i can be a value that increases as it approaches the focus position of the push pulse and decreases as it moves away from the focus position of the push pulse. This is because the closer to the push pulse focal length, the greater the energy of the shear wave and the higher the accuracy of the shear wave velocity. As an example of the weighting coefficient a _i , as indicated by a coefficient 461 in FIG. 8C, it may be 0 if the difference between the focal position of the push pulse (x coordinate is x _f ) and the x coordinate is a certain value or more. As shown by the coefficients 462 to 464 in FIG. 8C, an arbitrary function that increases as the difference between the focus position of the push pulse (x coordinate is x _f ) and the x coordinate may be used. In this way, it is possible to generate a velocity distribution diagram 450 that can confirm the entire appearance of the region 453 where the shear wave propagation velocity is high.

Finally, the propagation analysis unit 15 generates an elasticity image (step S460). Specifically, the elastic modulus is calculated from the velocity of the shear wave for each pixel of the velocity distribution diagram, and an elastic image is generated by associating each pixel with the elastic modulus. Coordinates (x _t, y _t) modulus at E (x _t, y _t), the speed of the shear wave in the coordinate v (x _t, y _t) with, can be calculated as follows.
E (x _t , y _t ) = 2 (1 + γ) ρ · v (x _t , y _t ) ²
Here, γ is the Poisson's ratio of the tissue at the coordinates (x _t , y _t ), and ρ is the density. For simplicity, for example, γ = 0.5 and ρ = 1 g / cm ³ may be calculated as follows.
E (x _t , y _t ) ≈3 · v (x _t , y _t ) ²
The association between each pixel and the elastic modulus is performed by mapping color information, for example. Thus, for example, as shown in FIG. 7B, coordinates whose elastic modulus is greater than a certain value are red, coordinates whose elastic modulus is less than a certain value are green, and coordinates where the elastic modulus could not be acquired are black, and so on. The elastic image 320 color-coded is generated. Classification is not limited to binarization, and classification and color classification may be performed at a predetermined stage. In FIG. 7B, a region 322 is a region whose elastic modulus is a certain value or more, and corresponds to the inclusion 321. In addition, in FIG.7 (b), although the inclusion 321 is clearly shown for description, the inclusion 321 does not appear directly on an actual elastic image. The propagation analysis unit 15 outputs the generated elasticity image to the control unit 11, and the control unit 11 outputs the elasticity image to the elasticity image storage unit 21.

  This completes the execution of the operation sequence. The subsequent processing will be described with reference back to FIG. Next, the control unit 11 displays an elastic image and an ultrasonic image (step S50). Specifically, the control unit 11 performs geometric transformation on the elasticity image generated in step S460 and the reference tomographic image signal acquired in step S420 so as to be image data for screen display, and after the geometric transformation. Are output to the display unit 3.

The control unit 11 accepts whether or not to continue the process from the user (inspector). If the process is continued, the process returns to step S10 to resume the process. If the process is not continued, the process is terminated (step S10). S70).
On the other hand, a case where the second operation sequence (step S60) is executed will be described. FIG. 9 is a flowchart showing details of the second operation sequence. The same operations as those in FIG. 3 are denoted by the same step numbers and description thereof is omitted. The second operation sequence is different from the steps S441, S445, and S450 in that steps S471, S475, and S480 are executed, and the number of executions of the subsequence including steps S471, S442, and S444 is different. Since this is the same as the operation sequence 1, the difference will be described below.

  In the second operation sequence, the number of sub-sequences is m (= 2), which is smaller than n (= 4), so that the focus position of the push pulse is also different from that in the first operation sequence. In step S471, the focal position of the first push pulse (i = 1) is, for example, the center of one small region obtained by dividing the region of interest into m (in this case, two divisions) in the column direction of the transducer. A specific example will be described with reference to FIG. The region of interest 407 is divided into four small regions 408 and 409, and the first push pulse is transmitted to the focal position 472 inside the small region 408. Similarly, the second push pulse (i = 2) is transmitted to the focal position 482 inside the small area 409.

  In addition, after the processing of all subsequences is completed (No in step S475), the propagation analysis unit 15 integrates the propagation analysis results (step S480). The specific processing is the same as in step S450, but the number of subsequences is different, so naturally the velocity distribution diagram is the first as shown in FIGS. 8 (d-1) and (d-2). There are only velocity distribution diagrams 470 and 480 relating to the sub-sequence and the second sub-sequence, respectively. In the velocity distribution diagram 470, the focus position 472 of the push pulse exists on the left side of the region of interest 471, and a region 473 where the shear wave propagation speed is high is detected. Similarly, in the velocity distribution diagram 480, the region of interest A focus position 482 of the push pulse exists on the right side of 421, and a region 483 where the shear wave propagation speed is high is detected. Similarly, the regions 473 and 483 having high shear wave propagation speeds actually correspond to one tissue. These are integrated to create one velocity distribution diagram 450 as shown in FIG. In this case, when the weighted average is used, the same weighting coefficient as in step S450 may be used. For example, the weighting coefficient is larger than in the case of step S450 even when the push pulse is away from the focal position. A specific coefficient, specifically, the coefficient 465 of FIG. 8C may be used. This is because there are fewer integration targets than in the case of step S450, and using a weighting coefficient that extracts only the vicinity of the focus of the push pulse may cause a region where the speed cannot be acquired. .

As described above, in the second sequence, the number of execution times of the subsequence is reduced as compared with the first sequence, so that the time required to generate one elastic image is about m / n times, that is, ½. It becomes possible to reduce. Therefore, the frame rate of the elastic image can be improved by about n / m times, that is, twice.
<Summary>
With the above configuration, when the moving speed of the ultrasonic probe is larger than the predetermined threshold, the operation sequence selection unit selects the second operation sequence in which the number of subsequences necessary for generating one elastic image is small. select. As a result, when the moving speed of the ultrasonic probe is high, the frame rate of the elastic image is improved, and the moving speed of the ultrasonic probe, which is the shift of the region of interest between the ultrasonic image and the elastic image, is improved. The influence of can be reduced. Furthermore, by improving the frame rate of the elastic image, it is possible to improve the followability to the movement of the ultrasonic probe. On the other hand, when the moving speed of the ultrasonic probe is equal to or lower than a predetermined threshold, the operation sequence selection unit selects the first operation sequence in which the number of subsequences necessary for generating one elastic image is large. To do. Thereby, when the moving speed of the ultrasonic probe is low, the accuracy of the elastic image can be improved. Therefore, the ultrasonic diagnostic apparatus according to the present embodiment can select and execute an optimal operation sequence in accordance with the moving speed of the ultrasonic probe.

<< Embodiment 2 >>
In the first embodiment, when the moving speed of the ultrasonic probe is larger than a predetermined threshold value, the second operation sequence in which the number of subsequences necessary for generating one elastic image is small is selected as the operation sequence. The case has been described in which the frame rate of the elastic image is improved by selection by the unit.

On the other hand, in this embodiment, a case where the frame rate of the elastic image is improved by another method will be described.
<Operation>
The operation of the ultrasonic diagnostic apparatus according to the second embodiment will be described. FIG. 10 is a flowchart showing the operation of the entire ultrasonic diagnostic apparatus. The same operations as those in FIG. 2 are denoted by the same step numbers and description thereof is omitted.

  In the second embodiment, when the moving speed of the ultrasonic probe is equal to or lower than a predetermined threshold (No in S30), the moving speed of the ultrasonic probe in the first embodiment is predetermined. The operation is exactly the same as when it is below the threshold. On the other hand, when the moving speed of the ultrasonic probe exceeds a predetermined threshold value (Yes in S30), a third sequence having a resolution lower than that of the first sequence is selected (step S40). Here, the resolution is a resolution related to transmission / reception of a detection wave after transmission of a push pulse, detection of displacement, and propagation analysis, which will be described in detail later.

  FIG. 11 is a flowchart showing details of the execution of the third sequence (step S90). The same operations as those in FIG. 3 are denoted by the same step numbers and the description thereof is omitted. The third sequence is different from the first sequence only in the operations of steps S492 to S494 related to the subsequence, the integration of the propagation analysis results related to step S510, and the elastic image generation operation related to step S520. Hereinafter, the operation of the third operation sequence will be described, but the same operation as the first operation sequence will be omitted, and only the above-described difference will be described.

  In the sub-sequence in the third operation sequence, push pulse transmission (S441) is the same as in the first operation sequence and the second operation sequence according to the first embodiment. On the other hand, transmission / reception of detected waves, displacement detection, and shear wave propagation analysis are performed with reduced resolution. This will be described in detail below. In the present embodiment, a case where the resolution is “spatially” low will be described.

  First, an ultrasonic wave with a reduced spatial resolution is transmitted / received a plurality of times in the region of interest, and the acquired plural ultrasonic signals are stored (step S492). Specifically, immediately after the end of the transmission of the push pulse, for example, the transmission / reception of the detection wave with the reduced spatial resolution is repeated 10,000 times per second. As a result, the tomographic image of the subject is repeatedly acquired immediately after the generation of the shear wave until the propagation ends. The operation related to each transmission event will be described in detail with reference to FIG. FIGS. 12A-1 and 12A-2 are schematic diagrams in the case where the transmission detection wave is a plane wave. When the transmission detection wave is a plane wave, in the transmission event according to the first operation sequence, for example, as shown in a schematic diagram 510, the entire transducer array of the ultrasonic probe so as to pass through the region of interest 511. Alternatively, the transmission detection wave 512 is transmitted using a continuous part. On the other hand, in the transmission event according to step S492, for example, as illustrated in a schematic diagram 520, among all or a continuous part of the transducer array of the ultrasonic probe so as to pass through the region of interest 521, Every other vibrator to be driven is selected, and the transmission detection wave 522 is transmitted using only the selected vibrator. Similarly, in the reception of the reflection detection wave, in the transmission event according to step S492, the transducers to be driven are selected from every other transducer array of the ultrasonic probe, and only the selected transducer is selected. The element reception signal is generated by using this, and the acoustic line signal is also generated by reducing the resolution in the x direction by half. On the other hand, FIGS. 12B-1 and 12B-2 are schematic diagrams when the transmission detection wave is a focal wave. When the transmission detection wave is a focal wave, in the transmission event according to the first operation sequence, for example, as shown in a schematic diagram 530, a series of focal waves 532 are transmitted so as to scan the region of interest 531. On the other hand, in the transmission event according to step S492, for example, as shown in a schematic diagram 540, the focus area 541 is set such that the movement pitch of the focal wave is doubled and the number of the series of focal waves 532 used for scanning is halved. Scan. In this case, since the phasing addition is performed every time a reflected detection wave for one focal wave is received, the resolution in the x direction of the acoustic line signal is inevitably reduced by half by reducing the number of focal waves. Note that the selection of elements related to plane wave transmission / reception is not limited to every other element, but may be every two or every three. Similarly, the moving pitch related to focal wave transmission / reception is not only doubled, but also tripled or quadrupled. But you can. By doing so, the spatial resolution in the x direction of the acoustic line signal is reduced to ½ to ¼. Accordingly, the calculation amount of the phasing addition for generating the acoustic line signal is ½ to 1. Decrease to / 4.

Returning to FIG. 11, the description will be continued. Next, the displacement is detected for each received signal (step S493). The specific operation is the same as that in step S443. However, since the resolution of the tomographic image signal in the x direction is low, the arithmetic processing is reduced, and the resolution in the x direction of the displacement image output as a result is similarly lowered.
Next, shear wave propagation analysis is performed (step S494). The specific operation is the same as in step S444, but since the resolution of the displacement image in the x direction is low, the arithmetic processing is reduced, and the spatial resolution of the resulting shear wave velocity is also reduced in the x direction.

  In addition, after the processing of all subsequences is completed (No in step S445), the propagation analysis unit 15 integrates the propagation analysis results (step S510). The specific process is the same as in step S450, but the spatial resolution of the shear wave velocity obtained in each subsequence is reduced in the x direction, so that the calculation process is reduced and the resulting shear wave is obtained. The spatial resolution of the velocity also decreases in the x direction.

Finally, the propagation analysis unit generates an elasticity image (step S520). The specific processing is the same as in step S460, but since the spatial resolution of the shear wave velocity is reduced in the x direction, the arithmetic processing is reduced, and as a result, the spatial resolution of the obtained elastic image is also in the x direction. To drop.
As described above, in the third sequence, the computation processing amount of the subsequence is reduced and the computation time is shortened compared to the first sequence. Specifically, the calculation amount of the phasing addition in step S492 and the calculation amounts related to all of steps S493 to S494 and 510 to S520 are reduced to ½ to ¼. For this reason, the time required to generate one elastic image can be shortened.

≪Modification≫
In the second embodiment, the case where the “spatial” resolution of detection wave transmission / reception, displacement detection, and shear wave propagation analysis is reduced in the sub-sequence in the third operation sequence has been described. On the other hand, in this modification, a case will be described in which the “temporal” resolution of detection wave transmission / reception, displacement detection, and shear wave propagation analysis is reduced in the sub-sequence of the third operation sequence.

  FIG. 13 is a flowchart showing details of the execution of the third sequence according to the present modification. The same operations as those in FIGS. 3 and 11 are denoted by the same step numbers and the description thereof is omitted. As for the third sequence according to this modification, the elastic image is generated in step S460 as in the first sequence, the operations in steps S495 to S497 related to the subsequence, and the propagation related to step S530. The integration of analysis results is different from the third sequence according to the second embodiment. Since the generation of the elastic image according to step S460 has already been described in the first embodiment, the other differences from the second embodiment will be described below.

  First, an ultrasonic wave is transmitted / received a plurality of times with a time interval increased in the region of interest, and a plurality of acquired ultrasonic signals are stored (step S495). Specifically, the detection wave with reduced time resolution is repeatedly transmitted and received immediately after the end of transmission of the push pulse, but the time resolution (frame rate) is the first sequence in order to increase the time interval of transmission and reception. Lower than step S442. This will be described in detail with reference to FIGS. 12 (c-1) and (c-2). FIG. 12C-1 is a schematic diagram illustrating step S442 according to the first operation sequence, in which p ultrasonic signals from the ultrasonic signal 550-1 to the ultrasonic signal 550-p are acquired. . The ultrasonic signal acquisition time interval Δta is, for example, 100 microseconds (10,000 times per second). On the other hand, FIG. 12C-2 is a schematic diagram illustrating step S492 according to the present modification, and q ultrasonic signals from the ultrasonic signal 560-1 to the ultrasonic signal 560-q are represented. get. The ultrasonic signal acquisition time interval Δtb is p / q times Δta, for example, 200 microseconds (5,000 times per second). That is, the start timing and the end timing of acquiring the ultrasonic signal are not changed in step S495 according to the present modification and step S442 according to the first operation sequence, and the acquisition time interval of the ultrasonic signals acquired continuously, That is, only the temporal resolution (frame rate) of the ultrasonic signal is different. By doing in this way, the number of ultrasonic signals to acquire can be reduced to q / p.

The description will be continued using FIG. 13 again. Next, the displacement is detected for each received signal (step S496). The specific operation is the same as in step S443, but since the number of received signals is reduced to q / p, the amount of calculation is reduced to q / p, and the number of obtained displacement images is similarly q / p. Decrease to p.
Next, shear wave propagation analysis is performed (step S497). The specific operation is the same as that in step S444. However, since the number of displacement images is reduced to q / p, the calculation amount is reduced to q / p.

  As described above, in the operation sequence according to the modified example, the calculation processing amount of the subsequence is reduced and the calculation time is shortened as compared with the first sequence. Specifically, the amount of computation for phasing addition in step S495 and the amount of computation for all of steps S496 to S497 are reduced to q / p. For this reason, the time required to generate one elastic image can be shortened.

<Summary>
With the above configuration, when the moving speed of the ultrasonic probe is higher than a predetermined threshold, the resolution (spatial and / or time) of transmission / reception of the detection wave after push pulse transmission, detection of displacement, and propagation analysis is achieved. The operation sequence selection unit selects a third operation sequence that is lower than the first operation sequence. Thereby, when the moving speed of the ultrasonic probe is high, the frame rate of the elastic image can be improved as in the first embodiment.

<< Embodiment 3 >>
In the first embodiment and the second embodiment, the case has been described in which the operation sequence is selected so as to improve the frame rate of the elastic image when the moving speed of the ultrasonic probe is larger than a predetermined threshold value.
In contrast, in the present embodiment, a case will be described in which an operation sequence having a different displacement detection method is selected when the moving speed of the ultrasonic probe is larger than a predetermined threshold value.

<Operation>
The operation of the ultrasonic diagnostic apparatus according to Embodiment 3 will be described. FIG. 14 is a flowchart showing the operation of the entire ultrasonic diagnostic apparatus. The same operations as those in FIGS. 2 and 10 are denoted by the same step numbers, and the description thereof is omitted.
In the third embodiment, when the moving speed of the ultrasonic probe is equal to or lower than a predetermined threshold (No in S30), the moving speed of the ultrasonic probe in the first embodiment is predetermined. The operation is exactly the same as when it is below the threshold. On the other hand, if the moving speed of the ultrasonic probe exceeds a predetermined threshold (Yes in S30), a fourth sequence for detecting displacement based on the difference between the received signals is selected (step S43).

FIG. 15 is a flowchart showing details of the execution of the fourth sequence (step S110). The same operations as those in FIG. 3 are denoted by the same step numbers and the description thereof is omitted. Regarding the fourth sequence, only the operation of step S523 related to displacement detection is different from the first sequence, and therefore the difference will be described below.
First, before describing the operation, the influence of the moving speed of the ultrasonic probe on the displacement detection will be described. FIGS. 16A and 16B are schematic diagrams when displacement detection is performed using two ultrasonic signals whose regions of interest do not match. As described above, the detection of displacement is performed by searching for corresponding points between the tomographic image signal that is the target of displacement detection and the reference tomographic image signal that is the reference, and detecting the difference in the coordinates of the corresponding points. . Then, for example, as shown in FIG. 16A, the attention area 602 of the tomographic image signal to be subjected to displacement detection is composed of the areas 603 and 605, and the attention area 601 of the reference tomographic image signal is the areas 603 and 604. In the region 603, the displacement can be detected, but in the region 605, no corresponding point exists in the reference ultrasonic signal, so that the displacement cannot be detected. Further, as shown in FIG. 16B, the attention area 607 of the tomographic image signal that is the target of displacement detection is composed of an area 608 and an area 610, and the attention area 606 of the reference tomographic image signal is the areas 608 and 609. , The overlapping area 608 is narrower than the area 603, and the area 609 where displacement cannot be detected is wider than the area 605. Although not shown here, if the tomographic image signal to be detected for displacement and the reference tomographic image signal do not overlap at all, the corresponding point cannot be detected, so that displacement cannot be detected at all. Things happen.

  Here, the tomographic image signal and the reference tomographic image signal used in the displacement detection method in step S443 according to the first operation sequence are reconfirmed. FIG. 16C is a diagram schematically showing a tomographic image signal and a displacement image. As described above, in step S443, the reference tomographic image signal acquired in step S420 executed before transmission of the push pulse is used. That is, for each of the tomographic image signals 621, 622, and 623 obtained in step S442, displacement images 631, 632, and 633 are generated using the reference tomographic image signal 620 obtained in step S420. Therefore, when the ultrasonic probe moves, the overlapping area of the region of interest becomes smaller as the time difference between the acquisition time of the tomographic image signal and the acquisition time of the reference tomographic image signal becomes larger. The problem that the rate of increase increases. As a result, it is difficult to analyze the propagation of a shear wave at a later time, that is, a place far from the focus position of the push pulse. Therefore, if the moving speed of the ultrasonic probe is high, it is far from the focus position of the push pulse. There arises a problem that the reliability of the result of elastic measurement of the place is lowered or the elastic measurement is impossible.

  On the other hand, the displacement detection method of step S543 according to the fourth operation sequence will be described below. FIG. 16D is a diagram schematically showing a tomographic image signal and a displacement image. In step S523, the reference tomographic image signal acquired in step S420 executed before the transmission of the push pulse is used for the first acquired tomographic image signal in the same manner as in step S443. However, for subsequent tomographic image signals, a tomographic image signal one frame before the tomographic image signal is used as a reference tomographic image signal, and a differential displacement image indicating a relative displacement for one frame is generated, and one frame before A displacement image corresponding to the tomographic image signal is generated by combining the displacement image corresponding to the tomographic image signal. This will be specifically described below. First, as for the tomographic image signal 621 acquired first, the displacement is detected with reference to the tomographic image signal 620 as in step S443, and a displacement image 631 is generated. On the other hand, with respect to the tomographic image signal 622, displacement is detected based on the tomographic image signal 621 one frame before, and a differential displacement image 642 is generated. Here, the displacement indicated by the differential displacement image 642 is a displacement between the tomographic image signal 622 and the tomographic image signal 621, in other words, the displacement image corresponding to the tomographic image signal 622 and the tomographic image signal 621. This is a difference from the displacement image 631. Therefore, a displacement image 652 corresponding to the tomographic image signal 622 can be obtained by performing a combination process in which the displacement amount corresponding to the same pixel is added to the displacement image 631 and the differential displacement image 642. Similarly, with respect to the tomographic image signal 623, a displacement is detected with reference to the tomographic image signal 623 of the previous frame, a differential displacement image 643 is generated, and the displacement image 652 and the differential displacement image 643 are synthesized. A displacement image 653 corresponding to the tomographic image signal 623 can be obtained. In this way, the difference in acquisition time between the reference image signal for obtaining the differential displacement image and the reference tomographic image signal is always small (one frame in the above example). Therefore, the ratio of the overlapping area in the region of interest can always be increased, and it is possible to avoid the enlargement of the region where displacement cannot be detected even if the moving speed of the ultrasonic probe is high. If the moving speed of the ultrasonic probe is low, the method has ideally the same displacement detection accuracy as the method of step S443, but actually the displacement detection accuracy is lower than that of step S443. There are many. This is because, as the time difference between the acquisition time of the tomographic image signal and the transmission time of the push pulse increases, it becomes necessary to synthesize a large number of differential displacement images. Therefore, errors included in the displacement amounts of the individual differential displacement images are accumulated by addition. It is to be done. Therefore, it is preferable to select the first operation sequence when the moving speed of the ultrasonic probe is low.

<Summary>
With the above configuration, when the moving speed of the ultrasonic probe is larger than the predetermined threshold, the operation sequence selection unit selects the fourth operation sequence for detecting the displacement based on the mutual difference of the received signals. Thereby, when the moving speed of the ultrasonic probe is high, it is possible to avoid the generation of a region where it is difficult to detect displacement.

<< Embodiment 4 >>
In the first to third embodiments, when the moving speed of the ultrasonic probe is larger than a predetermined threshold, the ultrasonic probe such as improving the frame rate of the elastic image or changing the displacement detection method. The case where the operation sequence that reduces the influence of the moving speed of the child is selected has been described.
In contrast, in the present embodiment, when the moving speed of the ultrasonic probe is larger than a predetermined threshold value, the elasticity measurement is performed after waiting for the moving speed of the ultrasonic probe to decrease. Select the operation sequence to start.

<Operation>
The operation of the ultrasonic diagnostic apparatus according to the fourth embodiment will be described. FIG. 17 is a flowchart showing the operation of the entire ultrasonic diagnostic apparatus. The same operations as those in FIG. 2 are denoted by the same step numbers and description thereof is omitted.
In the fourth embodiment, when the moving speed of the ultrasonic probe is equal to or lower than a predetermined threshold (No in S30), the moving speed of the ultrasonic probe in the first embodiment is predetermined. The operation is exactly the same as when it is below the threshold. On the other hand, if the moving speed of the ultrasonic probe exceeds a predetermined threshold value (Yes in S30), the fifth sequence that waits until the moving speed of the ultrasonic probe decreases is selected (Step S30). S44).

  FIG. 18 is a flowchart showing details of the execution of the fifth sequence (step S120). The same operations as those in FIG. 3 are denoted by the same step numbers and the description thereof is omitted. The fifth sequence is different from the first sequence in that steps S550 to S580 are added before setting the attention area (step S410). Hereinafter, only the difference between the fifth sequence and the first sequence will be described.

First, an ultrasonic wave is transmitted / received to / from the subject, the acquired received signal is stored (step S550), and then the moving speed of the ultrasonic probe is detected (step S560). Specific operations in steps S550 and S560 are the same as those in steps S10 and S20, respectively. Thereby, the moving speed of the ultrasonic probe can be calculated.
Next, it is determined whether or not the moving speed of the ultrasound probe has fallen below the second threshold value (step S570). The second threshold value is less than or equal to the predetermined threshold value in step S30. For example, both the predetermined threshold value and the second threshold value are 30 mm / s. Alternatively, for example, the predetermined threshold value may be 30 mm / s, and the second threshold value may be 10 mm / s.

  When the moving speed of the ultrasonic probe is equal to or higher than the second threshold (No in Step S570), only the B-mode image acquired in Step S550 is displayed (Step S580), and the process returns to Step S550 again. Measure the moving speed of the ultrasound probe. On the other hand, when the moving speed of the ultrasonic probe is lower than the second threshold value (Yes in step S570), the process proceeds to the setting of the region of interest in step S410. Therefore, the hardness of the subject can be evaluated after the moving speed of the ultrasonic probe falls below the second threshold value, and the shear wave in a state where the moving speed of the ultrasonic probe is high. Can be avoided.

<Summary>
With the above configuration, when the moving speed of the ultrasonic probe is larger than the predetermined threshold value, the sub-sequence is not started until the moving speed of the ultrasonic probe falls below the second threshold value. The operation sequence selection unit selects the fifth operation sequence to be performed. Therefore, when the moving speed of the ultrasonic probe is high, only the B-mode image is displayed, and the subsequence is not started until the moving speed of the ultrasonic probe is reduced. Thereby, it is possible to avoid shear wave propagation analysis when the moving speed of the ultrasonic probe is high.

<< Other Modifications According to Embodiment >>
(1) In the first to fourth embodiments and the modification, when the moving speed of the ultrasonic probe is larger than a predetermined threshold, one of the second to fifth operation sequences is selected. However, a sequence in which the second to fifth operation sequences are combined may be used. For example, when the moving speed of the ultrasonic probe is higher than a predetermined threshold value, an operation sequence with a small number of subsequences and a low spatial resolution of the detection wave may be used. By doing so, the frame rate of the elastic image can be further improved when the moving speed of the ultrasonic probe is larger than a predetermined threshold value. Or, for example, when the moving speed of the ultrasonic probe is larger than a predetermined threshold, the time resolution of the detection wave is low, and an operation sequence that detects displacement based on the mutual difference of the received signals is used. Also good. By doing this, when the moving speed of the ultrasonic probe is larger than a predetermined threshold, the area where displacement detection is impossible due to the low time resolution of the detection wave is easily expanded. It can be covered with the detection method. Alternatively, for example, when the moving speed of the ultrasonic probe is larger than a predetermined threshold value (30 mm / s), the moving speed of the ultrasonic probe becomes the second threshold value (10 mm / s). It is possible to stand by without starting the subsequence until it falls below, and the operation after the standby may be an operation sequence with a small number of subsequences. In this way, when the moving speed of the ultrasonic probe is slightly lower than the second threshold value, the ultrasonic diagnostic apparatus can be controlled according to the moving speed of the ultrasonic probe. . In addition, the combination of each embodiment and a modification is not restricted to the example mentioned above, You may combine arbitrarily, unless the combination which impairs the effect acquired.

  Note that the second to third operation sequences according to the first and second embodiments and the modified examples all improve the frame rate of the elastic image, but only one of them is applied or a combination of two or more is applied. In this case, b) is preferable to c) and a) is more preferable than b) for a) reducing the number of subsequences, b) reducing the spatial resolution of the detected wave, and c) reducing the temporal resolution of the detected wave. preferable. For example, when any one or more of the number of subsequences, the spatial resolution of the detection wave, or the temporal resolution of the detection wave is integrated to be ¼, the time resolution of the detection wave is less than ¼. The spatial resolution of the detection wave and the temporal resolution of the detection wave are both preferably halved, and the spatial resolution of the detection wave is more preferably ¼. In addition, it is preferable that both the spatial resolution of the detection wave and the number of subsequences are halved, and it is more preferable that the number of subsequences is ¼ than the spatial resolution of the detection wave is ¼. . This is due to the following reason. When the spatial resolution of the detection wave is lowered, the spatial resolution is lowered, the shear wave velocity error is increased, and the accuracy of the hardness evaluation value is lowered. On the other hand, when the time resolution of the detection wave is lowered, the shear wave velocity is averaged temporally and spatially, making it difficult to find the presence of a hard tissue and an interface with surrounding tissue. Therefore, regarding the resolution of the detection wave, the quality of the elastic image is less likely to deteriorate with the spatial resolution than with the temporal resolution. Even if the number of subsequences decreases, the quality of the elastic image does not deteriorate in a region where the amplitude of the shear wave is sufficiently large. Therefore, unlike the decrease in resolution of the detection wave, the quality of the elastic image does not necessarily deteriorate even if the number of subsequences decreases. Furthermore, even if the resolution of the detection wave is reduced to ¼, it is difficult to quadruple the frame rate because only the calculation time can be shortened in the time related to one operation sequence. On the other hand, if the number of subsequences is reduced to ¼, the time required for the subsequence occupying most of the time for one operation sequence is reduced to ¼ as it is, so the frame rate is almost quadrupled. It is possible to make it.

  (2) In Embodiments 1 to 4 and the modification, only one threshold value is used and only one operation sequence is selected from two types. However, a plurality of threshold values are used. Thus, an optimal operation sequence corresponding to the moving speed of the ultrasonic probe may be selected. For example, as shown in FIG. 19, a threshold A and a threshold B greater than the threshold A may be used. In this case, in step S31, when the moving speed of the ultrasonic probe is lower than the threshold value A, the first operation sequence is selected. When the moving speed of the ultrasonic probe is lower than the threshold value B and higher than the threshold value A, If the second operation sequence is equal to or greater than the threshold value B, the sixth operation sequence is selected. At this time, the threshold value A and the threshold value B are, for example, 10 mm / s and 20 mm / s, respectively. The sixth sequence is an operation sequence in which the second operation sequence and the third operation sequence are combined, that is, an operation sequence in which both the number of subsequences and the spatial resolution of the detection wave are reduced. In this way, it is possible to select an optimal operation sequence for the moving speed of the ultrasonic probe.

  Similarly, in the fifth sequence, a plurality of second threshold values may be used. For example, when the predetermined threshold value for selecting the fifth sequence is 30 mm / s, two second threshold values of 20 mm / s and 10 mm / s are used. When the moving speed of the ultrasonic probe is 10 mm / s or less, the same processing as in the first operation sequence is continued, and when the moving speed of the ultrasonic probe is greater than 10 mm / s and 20 mm / s or less. If there is, the same processing as in the second operation sequence is continued. In this way, it is possible to select an optimal operation sequence for the moving speed of the ultrasonic probe.

(3) In each of the embodiments and the modified examples, the case where the shear wave propagation analysis is performed by the procedure of the extraction of the displacement region, the thinning process, the spatial filtering, and the time filtering has been described. You may carry out in the procedure of a detection, temporal filtering, and spatial filtering.
(4) In each of the embodiments and modifications, the predetermined first operation sequence is used when the moving speed of the ultrasonic probe is equal to or lower than a predetermined threshold value. An operation sequence that is weak against movement of the child but improves measurement accuracy may be used. As an operation sequence that improves measurement accuracy, for example, a synthetic aperture method can be used in transmission and reception of a detection wave. By doing in this way, when the moving speed of an ultrasonic probe is small, the precision of evaluation of tissue hardness can be improved.

  (5) In each embodiment and modification, the displacement image or the differential displacement image is generated based on the difference between the tomographic image signal and the reference tomographic image signal. In generating the displacement image, correction may be performed by removing the moving speed of the ultrasound probe 2 from the displacement. This correction may be based on, for example, displacement of a position deeper or shallower than the focus position of the push pulse, as disclosed in Patent Document 1, or the ultrasonic probe 2 implemented in step S20. It may be equivalent to movement speed detection. For example, when the moving speed of the ultrasonic probe 2 is based on the measured value of a sensor built in the ultrasonic probe 2, the displacement may be corrected based on the measured value of the sensor.

  (6) In each embodiment and modification, when detecting the moving speed of the ultrasound probe 2 based on the tomographic image signal, the probe movement detecting unit 16 causes the latest tomographic image signal and the immediately preceding tomographic image to be detected. The moving speed of the ultrasound probe 2 is detected from the difference from the image signal. However, the present invention is not limited to this. For example, from the difference between the latest tomographic image signal and the tomographic image signal two frames before that The moving speed of the ultrasonic probe 2 may be detected. Alternatively, for example, the probe movement detection unit 16 causes the displacement detection unit 14 to detect the displacement of the latest tomographic image signal by using the tomographic image signal of one frame before (or more) the reference tomographic image signal as a reference image. The moving speed of the ultrasonic probe 2 may be detected based on the above.

  (7) In the first embodiment, the number of sub-sequences in the first operation sequence and the second operation sequence is 4 and 2, respectively. If the number of sub-sequences in the operation sequence is small, the number of sub-sequences may be arbitrary, such as 5, 3, for example. Note that the number of sub-sequences in the second operation sequence may be 1. In this case, the second operation sequence does not require steps S430, S445, and S446 related to the loop processing, and the propagation analysis result Since it is not necessary to perform integration, step S450 may not be included.

(8) In the first embodiment, the focal position of the push pulse is set to be completely different between the first operation sequence and the second operation sequence. However, the present invention is not limited to this case. For example, in the second operation sequence, The necessary number of push pulse focal positions in the first operation sequence may be selected as the push pulse focal position.
In any operation sequence, the focus position of the push pulse is not limited to the center of the small area. For example, an arbitrary position in the small area may be used as the focal position of the push pulse. Alternatively, for example, a small region may be set so that areas overlapping each other occur, and an arbitrary position in the small region may be used as the focus position of the push pulse.

  (9) In the second embodiment, when generating a reception signal by transmitting and receiving a detection wave with reduced spatial resolution, the transducer of the ultrasonic probe 2 used for transmission and reception of the detection wave is thinned out. However, thinning may be performed by other methods. For example, the transmission of the detection wave may be performed in the same manner as in step S442 related to the first operation sequence, and the transducer may be thinned only for reception of the reflected detection wave. Alternatively, for example, when generating an acoustic line signal by performing phasing addition without thinning out the transducer of the ultrasonic probe 2 used for transmission / reception of the detection wave, the step S442 according to the first operation sequence is performed. The acoustic line signal per tomographic image signal may be thinned out to ½ to ¼ by generating every two to four acoustic line signals in the transducer array direction (x direction).

Alternatively, thinning in the depth direction (y direction) may be performed when the acoustic line signal is generated by performing phasing addition. By doing so, the amount of calculation can be further reduced.
(10) In the fourth operation sequence according to the third embodiment, the differential displacement image corresponding to the tomographic image signal is generated on the basis of the previous tomographic image signal. The arbitrary tomographic image signal acquired in S442 may be used as a reference. By doing in this way, it becomes possible to reduce the frequency | count of composition of a differential displacement image, and a displacement error can be made small. Specifically, for example, with respect to the tomographic image signal of the 22nd frame acquired in step S442, the displacement image corresponding to the tomographic image signal of the first frame is changed to the tomographic image signal of the first frame and the tomographic image of the 11th frame. A differential displacement image of the signal, a differential displacement image of the tomographic image signal of the 11th frame and the tomographic image signal of the 21st frame, a differential displacement image of the tomographic image signal of the 21st frame and the tomographic image signal of the 22nd frame, By synthesizing three, the number of synthesis can be reduced to three.

  (11) In each embodiment and modification, the operation sequence is selected based on whether or not the moving speed of the ultrasound probe exceeds a predetermined threshold value. The operation sequence may be selected based on whether or not the moving speed of the acoustic probe exceeds a predetermined threshold value for a predetermined time or more. Here, the predetermined time is, for example, 3 seconds. Or, for example, regarding the moving speed of the ultrasonic probe, the operation sequence is selected based on whether or not both the latest instantaneous speed and the average speed for the last 3 seconds exceed a predetermined threshold value. Also good.

  Similarly, in the fifth sequence according to the fourth embodiment, for example, the subsequence may be started when the moving speed of the ultrasound probe is lower than the second threshold value for a predetermined time or more. . Alternatively, for example, with respect to the moving speed of the ultrasonic probe, the subsequence may be started when both the latest instantaneous speed and the average speed for the last 3 seconds are below the second threshold value. .

By doing so, the movement speed of the ultrasonic probe is temporarily lowered while the inspector is moving the ultrasonic probe, and the movement speed of the ultrasonic probe is small. It is possible to avoid erroneous detection and selecting an operation sequence that is not suitable for the moving speed of the ultrasonic probe or starting a sub-sequence.
(12) In the embodiment and each modification, the ultrasonic diagnostic apparatus generates and displays an elastic image for each operation sequence, but the present invention is not necessarily limited to this case. For example, the ultrasonic diagnostic apparatus may create an elastic image and store the elastic image in the elastic image storage unit and may not display the elastic image, or may output the elastic image to an external display device or an image processing device. You may go. Or, for example, the ultrasonic diagnostic apparatus only analyzes the shear wave propagation state for each operation sequence, and the analysis result of the shear wave propagation state such as a velocity distribution diagram indicating the shear wave velocity is stored in the elastic image storage unit. It may be memorized. In this case, the ultrasonic diagnostic apparatus may generate an elastic image from the analysis result of the propagation state of the shear wave as necessary. Alternatively, the ultrasonic diagnostic apparatus may output the analysis result of the propagation state of the shear wave to another apparatus, and the other apparatus may generate or display the elastic image.

In the embodiment and each modification, the ultrasonic diagnostic apparatus executes the next operation sequence after the end of one operation sequence, but the present invention is not necessarily limited to this case. For example, the ultrasonic diagnostic apparatus may execute the operation sequence, for example, a predetermined number of times or a number of times designated by the user.
(13) Although the ultrasonic diagnostic apparatus is configured to be connected to the display unit 3 in the embodiment and each modification, the present invention is not necessarily limited to this case. For example, the ultrasonic diagnostic apparatus 1 may include the display unit 3. Alternatively, the ultrasound diagnostic apparatus 1 is not connected to the display unit 3, and the elasticity image generated by the propagation analysis unit 15 and stored in the elasticity image storage unit 21 is stored in another storage medium, or another device is connected through a network. It may be output to.

Similarly, the ultrasonic diagnostic apparatus may include the ultrasonic probe 2, or the ultrasonic probe 2 includes an ultrasonic signal acquisition unit 13, and the ultrasonic signal acquisition unit 13. An ultrasonic diagnostic apparatus that does not have an acoustic line signal may acquire an acoustic line signal from the ultrasonic probe 2.
(14) The ultrasonic diagnostic apparatus according to the embodiment and each modified example may be realized in whole or in part by an integrated circuit of one chip or a plurality of chips, or by a computer program. It may be implemented in any other form. For example, the propagation analysis unit and the evaluation unit may be realized by one chip, only the ultrasonic signal acquisition unit may be realized by one chip, and the displacement detection unit and the like may be realized by another chip.

When realized by an integrated circuit, it is typically realized as an LSI (Large Scale Integration). The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.
Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

Further, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology.
Moreover, the ultrasonic diagnostic apparatus according to each embodiment and each modification may be realized by a program written in a storage medium and a computer that reads and executes the program. The storage medium may be any recording medium such as a memory card or a CD-ROM. Further, the ultrasonic diagnostic apparatus according to the present invention may be realized by a program downloaded via a network and a computer that downloads and executes the program from the network.

  (15) Each of the embodiments described above shows a preferred specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement positions and connection forms of the constituent elements, steps, order of steps, and the like shown in the embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the embodiment, steps that are not described in the independent claims indicating the highest concept of the present invention are described as arbitrary constituent elements constituting a more preferable form.

Further, for easy understanding of the invention, the scales of the components shown in the above-described embodiments may be different from actual ones. The present invention is not limited by the description of each of the above embodiments, and can be appropriately changed without departing from the gist of the present invention.
Furthermore, in the ultrasonic diagnostic apparatus, there are members such as circuit components and lead wires on the substrate, but various modes can be implemented based on ordinary knowledge in the technical field regarding electrical wiring and electrical circuits. Since it is not directly relevant to the description of the present invention, the description is omitted. Each figure shown above is a schematic diagram, and is not necessarily illustrated strictly.

<Supplement>
(1) The ultrasonic diagnostic apparatus according to the embodiment uses an ultrasonic probe to transmit a push pulse for concentrating ultrasonic waves on a specific part in a subject to physically press the tissue in the specific part After that, the ultrasonic wave is repeatedly transmitted and received within the subject to detect the propagation state of the shear wave having the pressed specific tissue as the vibration source in the region of interest set in the subject. An ultrasonic diagnostic apparatus that transmits a push pulse and transmits a detection wave to the subject a plurality of times following the push pulse and receives a reflected detection wave from the subject corresponding to the detection wave. Generating a plurality of reception signals in time series, and each of the detection times of the reflected detection waves, each detecting a displacement of the tissue in the subject due to the shear wave caused by the push pulse, Based on the detection result by the position detection unit, the propagation state of the shear wave in the region of interest is analyzed, and the elastic measurement unit for measuring the elasticity of each tissue in the subject and the moving speed of the ultrasonic probe are detected. A plurality of operation sequences that define a series of operations in which the push pulse transmission unit, the displacement detection unit, and the elasticity measurement unit cooperate with each other so that the probe movement detection unit and the elasticity measurement unit measure elasticity. A sequence holding unit for holding, and a sequence selection unit for selecting one operation sequence from a plurality of operation sequences held by the sequence holding unit based on a detection result of the probe movement detection unit. And

  In addition, the ultrasonic signal processing method according to the embodiment uses an ultrasonic probe to transmit a push pulse for concentrating the ultrasonic wave to a specific part in the subject to physically press the tissue in the specific part. After that, the ultrasonic signal for detecting the propagation state of the shear wave with the tissue at the pressed specific site as the vibration source in the region of interest in the subject by repeatedly transmitting and receiving the ultrasound to and from the subject. A processing method for detecting a moving speed of the ultrasonic probe and defining an operation sequence defining a series of operations for measuring elasticity in a region of interest in the subject. Select from a plurality of operation sequences that are held in advance based on the moving speed, based on the selected operation sequence, transmit a push pulse, and subsequently transmit a detection wave to the subject multiple times following the push pulse, A reflected detection wave from the subject corresponding to the outgoing wave is received to generate a plurality of reception signals in time series, and the inside of the subject due to the shear wave caused by the push pulse at each reception time of the reflected detection wave And detecting the elasticity of each tissue in the subject by analyzing the propagation state of the shear wave in the region of interest based on the displacement of the tissue in the subject. .

  According to the present disclosure, with the above-described configuration, the operation sequence for evaluating hardness can be changed based on the moving speed of the ultrasonic probe. Therefore, when the moving speed of the ultrasonic probe is high, for example, an operation sequence that is not affected by the movement of the ultrasonic probe can be selected. On the other hand, when the moving speed of the ultrasonic probe is low, for example, it is possible to select an operation sequence that is affected by the movement of the ultrasonic probe but improves the measurement accuracy. Thereby, the examiner can move the ultrasonic probe without worrying about the operation state of the ultrasonic diagnostic apparatus, and convenience is improved.

(2) In the ultrasonic diagnostic apparatus according to (1), the sequence selection unit may be configured such that, when the moving speed of the ultrasonic probe exceeds a predetermined speed, the ultrasonic wave corresponding to the measurement result of the elasticity measuring unit. The operation sequence may be selected so that the influence of the moving speed of the probe is reduced.
Thereby, regardless of the moving speed of the ultrasonic probe, it is possible to suppress the influence of the moving speed of the ultrasonic probe when the ultrasonic diagnostic apparatus detects the propagation state of the shear wave.

  (3) Further, the ultrasonic diagnostic apparatus of (2) described above has one elastic image showing the elasticity of each tissue in the subject based on the measurement result of the elasticity measuring unit for one operation sequence. An elastic image generating unit for generating the elastic image; and the sequence selecting unit selects an operation sequence so that a frame rate of the elastic image is improved when a moving speed of the ultrasonic probe exceeds the predetermined speed. It is good also as.

Thereby, when the moving speed of the ultrasonic probe is higher than a predetermined speed, the followability to the ultrasonic probe can be improved.
(4) In the ultrasonic diagnostic apparatus according to (2) to (3), the operation sequence includes transmission of one push pulse, detection of a displacement corresponding to the push pulse, and detection of the detected displacement. Elasticity measurement based on, and when the moving speed of the ultrasonic probe exceeds the predetermined speed, the sequence selection unit performs spatial processing, temporal The operation sequence may be selected so that the time required for one operation sequence is shortened by reducing at least one of the processing amounts.

This shortens the computation time for displacement detection and shear wave propagation analysis, thereby improving the frame rate of the elastic image, and the moving speed of the ultrasonic probe affects the detection of the propagation state of the shear wave. Can be deterred.
(5) In the ultrasonic diagnostic apparatus according to (2) to (3), the operation sequence includes two or more subsequences. Each subsequence includes transmission of one push pulse and the push Including displacement detection corresponding to the pulse and measurement of elasticity based on the detected displacement, the position where the push pulse is concentrated differs for each subsequence, and the operation sequence is based on the elasticity measured for each subsequence. The sequence selecting unit further includes: (a) when the moving speed of the ultrasonic probe exceeds the predetermined speed, in the displacement detecting unit In displacement detection, the time required for one subsequence is shortened by reducing at least one of the spatial processing amount and the temporal processing amount. (B) One movement Number of subsequence is reduced to be included in the sequence, select the operation sequence to satisfy at least one of may be.

As a result, the time required for a single motion sequence can be shortened by reducing the calculation time in displacement detection and shear wave propagation analysis and / or by reducing the number of subsequences, thereby improving the elastic image frame rate. It is possible to suppress the movement speed of the ultrasonic probe from affecting the detection of the propagation state of the shear wave.
(6) In the ultrasonic diagnostic apparatus according to (2) to (5), the operation sequence includes a time resolution indicating a frequency at which the displacement detection unit generates a reception signal and detects a displacement, and the displacement detection unit. Is defined by a parameter that specifies a spatial resolution indicating a spatial resolution when detecting displacement, and the sequence selection unit is configured to determine the temporal resolution when the moving speed of the ultrasonic probe exceeds the predetermined speed. The operation sequence may be selected so that at least one of the spatial resolutions becomes smaller.

  This makes it possible to reduce the amount of computation processing by performing displacement detection and shear wave propagation analysis sparsely in time or space, thereby shortening the computation time in displacement detection and shear wave propagation analysis. Thus, the frame rate of the elastic image can be improved, and the influence of the moving speed of the ultrasonic probe on the detection of the propagation state of the shear wave can be suppressed.

(7) In the ultrasonic diagnostic apparatus according to any one of (2) to (6), the sequence selection unit may be configured such that when the moving speed of the ultrasonic probe is equal to or lower than the predetermined speed, the displacement detection unit The operation sequence may be selected so that the spatial resolution of the received signal to be generated is improved.
Thereby, when the moving speed of the ultrasonic probe is equal to or lower than a predetermined speed, the propagation state of the shear wave can be detected with high accuracy.

  (8) Further, in the ultrasonic diagnostic apparatus according to (2) to (7), the sequence selection unit is configured to perform a first operation sequence when the moving speed of the ultrasonic probe exceeds a first speed. When the moving speed of the ultrasonic probe is equal to or lower than the first speed, and the second operation sequence is selected, the moving speed of the ultrasonic probe is set to the first speed. When the second speed, which is higher than the second speed, is exceeded, the third operation sequence may be selected instead of the first operation sequence.

Thereby, it is possible to select an optimal operation sequence for the moving speed of the ultrasonic probe.
(9) In the ultrasonic diagnostic apparatus according to (1), the sequence selection unit may be configured such that when the moving speed of the ultrasonic probe exceeds the first speed, the ultrasonic probe It is also possible to select an operation sequence that does not start the operation sequence until the moving speed becomes equal to or lower than the second speed.

As a result, when the moving speed of the ultrasonic probe is large, the ultrasonic diagnostic device detects the propagation state of the shear wave by waiting until the moving speed of the ultrasonic probe is reduced. The influence of the moving speed of the probe can be suppressed.
(10) In the ultrasonic diagnostic apparatus according to (9), the second speed may be equal to or lower than the first speed.

Thereby, the ultrasonic diagnostic apparatus can detect the propagation state of the shear wave after the moving speed of the ultrasonic probe is lowered until the moving speed of the ultrasonic probe is not affected.
(11) In the ultrasonic diagnostic apparatus according to (1), the sequence selection unit may be configured such that the displacement detection unit detects the push pulse when the moving speed of the ultrasonic probe is equal to or lower than a predetermined speed. A reference signal is generated before transmission and a displacement is detected using a difference between the reference signal and the received signal, and when the moving speed of the ultrasonic probe exceeds the predetermined speed, The operation sequence may be selected so that the displacement detection unit detects a displacement by using a difference between a plurality of reception signals that are continuous in time series as a displacement change amount.

Thereby, when the moving speed of the ultrasonic probe is high, it is possible to detect the displacement so that the detectable area of the displacement does not decrease.
(12) In the ultrasonic diagnostic apparatus according to (1) to (11), the probe movement detection unit is configured to detect the ultrasonic probe based on a received signal acquired using the ultrasonic probe. It is good also as detecting the moving speed of a child.

Accordingly, the moving speed of the ultrasonic probe can be detected without providing a sensor or the like on the ultrasonic probe.
(13) In the ultrasonic diagnostic apparatus according to (1) to (11), the probe movement detection unit is based on a signal acquired from a sensor provided inside or outside the ultrasonic probe. Then, the moving speed of the ultrasonic probe may be detected.

  Thereby, the calculation of the moving speed of the ultrasonic probe is not required in the ultrasonic diagnostic apparatus, and the moving speed of the ultrasonic probe can be detected more accurately.

  The ultrasonic diagnostic apparatus and the ultrasonic signal processing method according to the present disclosure are useful for measurement of tissue hardness using ultrasonic waves. Therefore, it becomes possible to improve the measurement accuracy of tissue hardness, and has high applicability in medical diagnostic equipment and the like.

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus 2 Ultrasonic probe 3 Display part 11 Control part 12 Shear wave excitation part 13 Ultrasonic signal acquisition part 14 Displacement detection part 15 Propagation analysis part 16 Probe movement detection part 17 Sequence selection part 18 Tomographic image Storage unit 19 Displacement amount storage unit 20 Sequence holding unit 21 Elastic image storage unit

Claims (14)

Using an ultrasound probe, send a push pulse that concentrates the ultrasound at a specific site in the subject to physically press the tissue at the specific site, and then repeatedly send and receive ultrasound to and from the subject An ultrasonic diagnostic apparatus that detects a propagation state in a region of interest set in the subject of a shear wave using a tissue of a pressed specific site as a vibration source by
A push pulse transmitter for transmitting a push pulse;
A detection wave is transmitted to the subject a plurality of times following the push pulse, a reflected detection wave from the subject corresponding to the detection wave is received, a plurality of reception signals are generated in time series, and the reception time of the reflected detection wave A displacement detector for detecting a displacement of tissue in the subject due to a shear wave caused by the push pulse, respectively,
Based on the detection result by the displacement detection unit, analyze the propagation state of the shear wave in the region of interest, and measure the elasticity of each tissue in the subject,
A probe movement detector for detecting the moving speed of the ultrasonic probe;
A sequence holding unit that holds a plurality of operation sequences that define a series of operations in which the push pulse transmission unit, the displacement detection unit, and the elasticity measurement unit cooperate to measure elasticity of the elasticity measurement unit;
An ultrasonic diagnostic apparatus comprising: a sequence selection unit that selects one operation sequence from a plurality of operation sequences held by the sequence holding unit based on a detection result of the probe movement detection unit. When the moving speed of the ultrasonic probe exceeds a predetermined speed, the sequence selection unit sets an operation sequence so that the influence of the moving speed of the ultrasonic probe on the measurement result of the elasticity measuring unit is reduced. The ultrasonic diagnostic apparatus according to claim 1, wherein the ultrasonic diagnostic apparatus is selected. An elastic image generating unit that generates one elastic image showing the elasticity of each tissue in the subject based on the measurement result of the elastic measuring unit for one operation sequence;
The said sequence selection part selects an operation | movement sequence so that the frame rate of the said elastic image may improve, when the moving speed of the said ultrasound probe exceeds the said predetermined speed. Ultrasound diagnostic equipment. The operation sequence includes transmission of one push pulse, detection of a displacement corresponding to the push pulse, and measurement of elasticity based on the detected displacement,
The sequence selection unit reduces at least one of a spatial processing amount and a temporal processing amount in displacement detection in the displacement detection unit when the moving speed of the ultrasonic probe exceeds the predetermined speed. The ultrasonic diagnostic apparatus according to claim 2 or 3, wherein the operation sequence is selected so that the time required for one operation sequence is shortened. The operation sequence includes two or more subsequences,
Each of the subsequences includes transmission of one push pulse, detection of a displacement corresponding to the push pulse, and measurement of elasticity based on the detected displacement,
The position where the push pulses are concentrated differs for each subsequence.
The operation sequence further includes a process of measuring the elasticity of each tissue in the subject based on the elasticity measured for each subsequence,
The sequence selection unit is (1) when the movement speed of the ultrasonic probe exceeds the predetermined speed, in the displacement detection in the displacement detection unit, at least one of a spatial processing amount and a temporal processing amount Select one of the operation sequences to satisfy at least one of the following: (2) The number of sub-sequences included in one operation sequence decreases. The ultrasonic diagnostic apparatus according to claim 2 or 3, wherein: The operation sequence is defined by a parameter that specifies a time resolution indicating a frequency at which the displacement detection unit generates a reception signal and detects a displacement, and a spatial resolution indicating a spatial resolution when the displacement detection unit detects a displacement. And
The sequence selection unit selects an operation sequence so that at least one of the temporal resolution and the spatial resolution becomes smaller when the moving speed of the ultrasonic probe exceeds the predetermined speed. The ultrasonic diagnostic apparatus according to any one of claims 2 to 5. The sequence selection unit selects an operation sequence so that a spatial resolution of a reception signal generated by the displacement detection unit is improved when a moving speed of the ultrasonic probe is equal to or lower than the predetermined speed. The ultrasonic diagnostic apparatus according to any one of claims 2 to 6. The sequence selection unit selects the first operation sequence when the moving speed of the ultrasonic probe exceeds the first speed, and the moving speed of the ultrasonic probe is equal to or lower than the first speed. When the second operation sequence is selected when the movement speed of the ultrasonic probe exceeds the second speed which is higher than the first speed, the first operation is performed. The ultrasonic diagnostic apparatus according to any one of claims 2 to 7, wherein a third operation sequence is selected instead of the sequence. When the moving speed of the ultrasonic probe exceeds the first speed, the sequence selection unit starts an operation sequence until the moving speed of the ultrasonic probe becomes equal to or lower than the second speed. The ultrasonic diagnostic apparatus according to claim 1, wherein an operation sequence that does not occur is selected. The ultrasonic diagnostic apparatus according to claim 9, wherein the second speed is equal to or lower than the first speed. When the moving speed of the ultrasound probe is equal to or lower than a predetermined speed, the sequence selection unit generates a reference signal before the push pulse is transmitted, and the reference signal and the reception When the displacement is detected using a difference from the signal and the moving speed of the ultrasonic probe exceeds the predetermined speed, the displacement detector detects a difference between a plurality of received signals that are continuous in time series. The ultrasonic diagnostic apparatus according to claim 1, wherein an operation sequence is selected so that the displacement is detected by using the displacement as a change amount. The said probe movement detection part detects the moving speed of the said ultrasonic probe based on the received signal acquired using the said ultrasonic probe. The one of the Claims 1 thru | or 11 characterized by the above-mentioned. The ultrasonic diagnostic apparatus according to item 1. The said probe movement detection part detects the moving speed of the said ultrasound probe based on the signal acquired from the sensor provided in the inside or the exterior of the said ultrasound probe. The ultrasonic diagnostic apparatus according to any one of 1 to 11. Using an ultrasound probe, send a push pulse that concentrates the ultrasound at a specific site in the subject to physically press the tissue at the specific site, and then repeatedly send and receive ultrasound to and from the subject An ultrasonic signal processing method for detecting a propagation state of a shear wave using a tissue of a pressed specific part as a vibration source in a region of interest in the subject,
Detecting the moving speed of the ultrasonic probe,
An operation sequence that defines a series of operations for measuring elasticity in a region of interest in the subject is selected from a plurality of operation sequences that are held in advance based on the moving speed of the ultrasonic probe,
Based on the selected operation sequence,
Send a push pulse,
A detection wave is transmitted to the subject a plurality of times following the push pulse, a reflected detection wave from the subject corresponding to the detection wave is received, a plurality of reception signals are generated in time series, and the reception time of the reflected detection wave Detecting the displacement of the tissue in the subject due to the shear wave caused by the push pulse,
An ultrasonic signal processing method, comprising: analyzing a state of propagation of a shear wave in the region of interest based on a displacement of a tissue in the subject and measuring elasticity of each tissue in the subject.

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